This invention relates to fluid separation and permeation.
One method of permeation separation involves electrodialysis wherein the solution to be demineralized is fed into one or more cells defined by ion-selective membranes. When an electric field is applied across the separation cells, negative ions are drawn through anion-permeable membranes toward the cathode, while positive ions are drawn through cation-permeable membranes toward the anode whereby the feed solution is continually deionized.
One prior art type of separation apparatus employs filtration membranes in combination with electrodialysis cells for the removal of relatively large particles in addition to ionic particles. This type of apparatus is effective for separating the constituents of protein solutions such as cheese whey which proteins, lactose and minerals, commonly referred to as ash. The protein is separated by the filtration membranes while the anion and cation membranes separate the lactose from the ash which is typically potassium cholride. However, such protein solutions also typically include other anionic materials, such as weakly ionized amino acids, which tend to ineversibly foul anion membrances.